[Gegl-developer] gegl-demo & region of interest

[Øyvind Kolås]

On 6/27/06, Richard Kralovic <Richard.Kralovic at inf.ethz.ch> wrote:
> I changed the definition of REMAINDER to this:
> #define REMAINDER(dividend, divisor)         \
>    ((((dividend)%(divisor) < 0) ?                      \
>    (divisor) - ((-(dividend)) % (divisor)) : \
>    ((dividend) % (divisor))))
> Is this the right fix?

The new version of the tile_offset function (earlier toff) using the
REMAINDER macro is indeed buggy. Your fix is almost correct, the
coorect fix was:

#define REMAINDER(dividend, divisor)                       \
   ((((dividend) < 0) ?                                    \
   ((divisor) - ((-(dividend)) % (divisor))) % (divisor) : \
   ((dividend) % (divisor))))

(the whole point of this macro is that the result of %'ing a negative
number is not defined in C, thus using it in the computation doesn't
seem the right thing to do ;)

/Øyvind K.
-- 
«The future is already here. It's just not very evenly distributed»
                                                 -- William Gibson
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